1. Field of the Invention
The invention relates to an apparatus for drilling a deviated bore hole and for drilling a straight section of bore hole which may be horizontal or at any angle from the terminus of a small radius curved bore hole.
2. Prior Art
There have been many efforts to develop apparatus for successfully drilling small radius deviated well bores. Prominent among those working in this field was J. A. Zublin, to whom many patents have issued. Typical of his efforts in this field is U.S. Pat. No. 2,631,820, which teaches the use of a curved drill guide to maintain a curved drill course in spite of radial forces working against the drill guide. Included in the use of the drill guide is a heavy duty flexible drill pipe as taught in U.S. Pat. No. 2,515,366.
Zublin again directed his attention to a curved drill guide in U.S. Pat. No. 2,664,270. In addition, this patent teaches the use of a rib, attached to the outside of the drill guide, to help stabilize the guide while rotating the flexible drill pipe of U.S. Pat. No. 2,515,366. The patentee used two or more ribs attached to the bottom end of the drill guide, as shown in the drawings, in order to limit the curvature of the well bore. Otherwise, there was a tendency to form a U-shaped well bore.
In U.S. Pat. No. 2,669,430, the patentee taught an apparatus for drilling devitated well bores utilizing a number of straight tubular drill guide sections. These so-called "straight" drill guide sections were stacked on the sectional drill collars, end to end, and designed so that the drill guide sections were rotatable relative to each other. Used in conjunction with a whipstock, they imparted flexibility to the drill string on making the curved drill path but became rigid for lateral drilling.
Another Zublin patent, U.S. Pat. No. 2,672,321, discloses a clutch mechanism useful with the curved drill guide of U.S. Pat. No. 2,515,366. The drill guide and clutch mechanism carried the drill string weight during drilling operations. In practice, the bearings of this clutch were not able to withstand the thrust loads required in normal drilling operations.
Other art in this field is represented in the following U.S. Pat. Nos.
2,336,338 PA1 2,344,277 PA1 2,402,003 PA1 2,515,365 PA1 2,634,097 PA1 2,684,581
2,680,358